This relates generally to electronic devices and, more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones, computers, and televisions have displays. The center of a display such as a liquid crystal display contains an array of pixels. This portion of the display, which is sometimes referred to as the active area of the display, is used to display images to a user. Peripheral circuits and other portions of the display that do not display images form a border that surrounds the active area. This border is sometimes referred to as the border area of the display.
A conventional liquid crystal display includes a thin-film transistor layer, a color filter layer, and liquid crystal material interposed between the thin-film transistor layer and the color filter layer. A ring of epoxy is formed along the border of the display to help encapsulate the liquid crystal material between the thin-film transistor layer and the color filter layer.
The thin-film transistor layer typically includes a glass substrate, an oxide layer formed on the glass substrate, and an organic planarization layer formed on the oxide layer. The presence of the organic planarization layer in the border area is, however, susceptible to moisture leakage (i.e., moisture can sometimes seep through the interface of the planarization layer and oxide layer). As a result, a portion of the planarization layer has to be removed in the border area to form a trench region that is devoid of the planarization material. This trench region may help provide good adhesion for the epoxy while providing moisture blocking.
To save cost, some liquid crystal displays are fabricated using a mask that patterns both the oxide layer and the planarization layer simultaneously. In such displays, it may not be possible to place active metal routing structures within the trench region since the active metal routing structures may be subject to oxide undercutting during the formation of the moisture blocking trench, which can substantially degrade the mechanical stability of those metal routing structures. Moving all metal routing structures out of the moisture blocking trench region will, however, substantially increase the border area of the display.
It would therefore be desirable to be able to provide electronic devices with improved display structures having smaller display borders while providing adequate moisture blocking.